1. Field of the Invention
The present invention relates to an improvement in a jigger dyeing apparatus.
2. Description of the Prior Art
In the known jigger dyeing apparatus, a travel passage of a spread textile fabric to be dyed is defined by two winding rolls arranged in parallel in a can and several movable rolls arranged below the winding rolls in parallel thereto, and the lowermost roll is immersed in a dyeing solution contained in a dyeing box. In the dyeing process using this jigger dyeing apparatus, a web of textile fabric to be dyed, which is wound on one winding roll (hereinafter referred to as "winding roll A") is unwound and passed through the above-mentioned travel passage, and the fabric is then wound on the other winding roll (hereinafter referred to as "winding roll B"). This operation is continued until the fabric is entirely wound on the winding roll B. Then, the fabric wound on the roll B is wound in the reverse direction, and the fabric is entirely wound on the winding roll A again through the travel passage. This travel of the fabric between both the winding rolls is repeated several times, whereby the fabric is subjected to winding and dipping repeatedly and is dyed. The serious defect of this dyeing process is that the central portion of the fabric with respect to the weft direction is dyed more thinly than both the selvage portions. That is, so-called listing is caused. Various methods have been adopted for preventing occurrence of listing, but no good results have been obtained.
We made research with a view to solving this problem of listing in the jigger dyeing process, and it was found that listing is caused for the following two reasons.
In the first place, between the central portion and both the selvage portions of a spread fabric, wound on the winding rolls, with respect to the weft direction, there are differences of the amount of the dyeing solution impregnated in the fabric and the amount of the dyeing solution present between the layers of the wound fabric. In short, the difference of the retention quantity of the dyeing solution is one cause of listing. When the fabric dipped in the dyeing solution is wound on the winding roll, a part of the dyeing solution taken out together with the fabric is dropped into the dyeing box by squeezing, and simultaneously, the remaining dyeing solution flows toward both the selvage portions and is left in the selvage portions. Accordingly, the retention quantity of the dyeing solution in the selvage portions becomes larger than in the central portion, with the result that the central portion having a smaller retention quantity of the dyeing solution is dyed more thinly than the selvage portions having a larger retention quantity of the dyeing solution.
In the second place, when the fabric is dipped in the dyeing solution, the dye concentration in the dye solution that comes in contact with the fabric differs between the central portion and both the selvage portions with respect to the weft direction. This difference of the dye concentration is another cause of listing. The dyeing solution left in both the selvage portions of the fabric in the dyeing box with respect to the weft direction does not permeate through the fabric even after the dye has been absorbed in the fabric, and the residual dyeing solution is replaced in succession with the fresh dyeing solution from the outer side, with the result that the dye concentration is hardly reduced. On the other hand, the dyeing solution present in the central portion is hardly replaced by the fresh dyeing solution, and therefore, the dye concentration is graudally reduced and the dye concentration is always lower than in the dyeing solution present in both the selvage portions. Accordingly, the central portion of the fabric is dyed more thinly than the selvage portions.
We found that listing is caused mainly for the above-mentioned two reasons, and we have now completed the present invention.